1. Technical Field
The techniques described herein relate generally to wireless power delivery, and particularly to calibration of wireless transmission strength to accommodate wireless power transfer through a surface at which a wireless power transmitter is installed.
2. Discussion of the Related Art
Wireless Power Transfer Systems (WPTS) are gaining increasing popularity as convenient way to deliver power without wires or connectors. WPTS currently under development in the industry can be separated in two major classes: magnetic induction (MI) systems and magnetic resonance (MR) systems. Both types of systems include a transmitting unit, sometimes referred to as a power transmitting unit (PTU), and a receiving unit, sometimes referred to as a power receiving unit (PRU). Such systems can be used to wirelessly power or charge mobile devices such as smartphones, portable music players, tablets, and laptops, among other devices and applications.
Inductive WPTS typically operate in an allocated frequency range of several hundred kilohertz using frequency variation as a power flow control mechanism. MR WPTS typically operate on a single resonant frequency using input voltage regulation to regulate output power. In typical applications, MR WPTS operate at a frequency of 6.78 MHz.
Several industry committees such as the Wireless Power Consortium (WPC), the recently-merged Power Matters Alliance (PMA), and the Alliance for Wireless Power (A4WP), collectively A4WP/PMA, are working on developing international standards for consumer products based on wireless power transfer. The standards may include specifications on an amount of rectified current, voltage, and/or power generated at a PRU via the device's receiving coil and power rectification circuitry. The standards may also include specifications on a distance between a transmitting coil of a PTU and a receiving coil of a PRU.